Fine dissection electrosurgical device

ABSTRACT

An electrosurgical wand. At least some of the illustrative embodiments are electrosurgical wands including an elongate shaft that defines a handle end and a distal end, a first discharge aperture on the distal end of the elongate shaft, a first active electrode of conductive material disposed on the distal end of the elongate shaft, the first active electrode has an edge feature, a first return electrode of conductive material disposed a substantially constant distance from the first active electrode, and an aspiration aperture on the distal end of the elongate shaft fluidly coupled to a second fluid conduit.

BACKGROUND

The field of electrosurgery includes a number of loosely relatedsurgical techniques which have in common the application of electricalenergy to modify the structure or integrity of patient tissue.Electrosurgical procedures usually operate through the application ofvery high frequency currents to cut or ablate tissue structures, wherethe operation can be monopolar or bipolar. Monopolar techniques rely ona separate electrode for the return of current that is placed away fromthe surgical site on the body of the patient, and where the surgicaldevice defines only a single electrode pole that provides the surgicaleffect. Bipolar devices comprise two or more electrodes on the samesupport for the application of current between their surfaces.

Electrosurgical procedures and techniques are particularly advantageoussince they generally reduce patient bleeding and trauma associated withcutting operations. Additionally, electrosurgical ablation procedures,where tissue surfaces and volume may be reshaped, cannot be duplicatedthrough other treatment modalities.

Radiofrequency (RF) energy is used in a wide range of surgicalprocedures because it provides efficient tissue resection andcoagulation and relatively easy access to the target tissues through aportal or cannula. Conventional monopolar high frequency electrosurgicaldevices typically operate by creating a voltage difference between theactive electrode and the target tissue, causing an electrical arc toform across the physical gap between the electrode and tissue. At thepoint of contact of the electric arcs with tissue, rapid tissue heatingoccurs due to high current density between the electrode and tissue.This high current density causes cellular fluids to rapidly vaporizeinto steam, thereby producing a “cutting effect” along the pathway oflocalized tissue heating. Thus, the tissue is parted along the pathwayof evaporated cellular fluid, inducing undesirable collateral tissuedamage in regions surrounding the target tissue site. This collateraltissue damage often causes indiscriminate destruction of tissue,resulting in the loss of the proper function of the tissue. In addition,the device does not remove any tissue directly, but rather depends ondestroying a zone of tissue and allowing the body to eventually removethe destroyed tissue.

Present electrosurgical techniques used for tissue ablation may sufferfrom an inability to provide the ability for fine dissection of softtissue. The distal end of electrosurgical devices is wide and flat,creating a relatively wide area of volumetric tissue removal and makingfine dissections along tissue planes more difficult to achieve becauseof the lack of precision provided by the current tip geometries. Inaddition, identification of the plane is more difficult because thelarge ablated area and overall size of the device tip obscures thephysician's view of the surgical field. The inability to provide forfine dissection of soft tissue is a significant disadvantage in usingelectrosurgical techniques for tissue ablation, particularly inarthroscopic, otolaryngological, and spinal procedures.

Traditional monopolar RF systems can provide fine dissectioncapabilities of soft tissue, but may also cause a high level ofcollateral thermal damage. Further, these devices may suffer from aninability to control the depth of necrosis in the tissue being treated.The high heat intensity generated by these systems causes burning andcharring of the surrounding tissue, leading to increased pain and slowerrecovery of the remaining tissue. Further, the desire for anelectrosurgical device to provide for fine dissection of soft tissue maycompromise the ability to provide consistent ablative cutting withoutsignificant collateral damage while allowing for concomitant hemostasisand good coagulation of the remaining tissue.

Accordingly, improved systems and methods are still desired forperforming fine dissection of soft tissue via electrosurgical ablationof tissue. In particular, improved systems operable to provide acombination of smooth and precise cutting, effective concomitanthemostasis during cutting, and efficient coagulation ability in finedissection soft tissue procedures would provide a competitive advantage.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of exemplary embodiments, reference will nowbe made to the accompanying drawings in which:

FIG. 1 shows an electrosurgical system in accordance with at least someembodiments;

FIG. 2A shows a perspective view a portion of a wand in accordance withat least some embodiments;

FIG. 2B shows an end elevation view of a wand in accordance with atleast some embodiments;

FIG. 2C shows a cross-sectional view of a wand in accordance with atleast some embodiments;

FIG. 3A shows a side elevation view of a wand in accordance with atleast some embodiments;

FIG. 3B shows a side elevation view of a wand in accordance with atleast some embodiments;

FIG. 3C shows a cross-sectional view of a wand in accordance with atleast some embodiments;

FIG. 4A shows a cross-sectional view of a wand in accordance with atleast some embodiments;

FIG. 4B shows a cross-sectional view of a wand in accordance with atleast some embodiments;

FIG. 5 shows both an elevational end-view (left) and a cross-sectionalview (right) of a wand connector in accordance with at least someembodiments;

FIG. 6 shows both an elevational end-view (left) and a cross-sectionalview (right) of a controller connector in accordance with at least someembodiments;

FIG. 7 shows an electrical block diagram of an electrosurgicalcontroller in accordance with at least some embodiments; and

FIG. 8 shows a method in accordance with at least some embodiments.

NOTATION AND NOMENCLATURE

Certain terms are used throughout the following description and claimsto refer to particular system components. As one skilled in the art willappreciate, companies that design and manufacture electrosurgicalsystems may refer to a component by different names. This document doesnot intend to distinguish between components that differ in name but notfunction.

In the following discussion and in the claims, the terms “including” and“comprising” are used in an open-ended fashion, and thus should beinterpreted to mean “including, but not limited to . . . ” Also, theterm “couple” or “couples” is intended to mean either an indirect ordirect connection. Thus, if a first device couples to a second device,that connection may be through a direct connection or through anindirect electrical connection via other devices and connections.

Reference to a singular item includes the possibility that there areplural of the same items present. More specifically, as used herein andin the appended claims, the singular forms “a,” “an,” “said” and “the”include plural references unless the context clearly dictates otherwise.It is further noted that the claims may be drafted to exclude anyoptional element. As such, this statement serves as antecedent basis foruse of such exclusive terminology as “solely,” “only” and the like inconnection with the recitation of claim elements, or use of a “negative”limitation. Lastly, it is to be appreciated that unless definedotherwise, all technical and scientific terms used herein have the samemeaning as commonly understood by one of ordinary skill in the art towhich this invention belongs.

“Active electrode” shall mean an electrode of an electrosurgical wandwhich produces an electrically-induced tissue-altering effect whenbrought into contact with, or close proximity to, a tissue targeted fortreatment.

“Return electrode” shall mean an electrode of an electrosurgical wandwhich serves to provide a current flow path for electrons with respectto an active electrode, and/or an electrode of an electrical surgicalwand which does not itself produce an electrically-inducedtissue-altering effect on tissue targeted for treatment.

A fluid conduit said to be “within” an elongate shaft shall include notonly a separate fluid conduit that physically resides within an internalvolume of the elongate shaft, but also situations where the internalvolume of the elongate shaft is itself the fluid conduit.

Where a range of values is provided, it is understood that everyintervening value, between the upper and lower limit of that range andany other stated or intervening value in that stated range isencompassed within the invention. Also, it is contemplated that anyoptional feature of the inventive variations described may be set forthand claimed independently, or in combination with any one or more of thefeatures described herein.

All existing subject matter mentioned herein (e.g., publications,patents, patent applications and hardware) is incorporated by referenceherein in its entirety except insofar as the subject matter may conflictwith that of the present invention (in which case what is present hereinshall prevail). The referenced items are provided solely for theirdisclosure prior to the filing date of the present application. Nothingherein is to be construed as an admission that the present invention isnot entitled to antedate such material by virtue of prior invention.

DETAILED DESCRIPTION

Before the various embodiments are described in detail, it is to beunderstood that this invention is not limited to particular variationsset forth herein as various changes or modifications may be made, andequivalents may be substituted, without departing from the spirit andscope of the invention. As will be apparent to those of skill in the artupon reading this disclosure, each of the individual embodimentsdescribed and illustrated herein has discrete components and featureswhich may be readily separated from or combined with the features of anyof the other several embodiments without departing from the scope orspirit of the present invention. In addition, many modifications may bemade to adapt a particular situation, material, composition of matter,process, process act(s) or step(s) to the objective(s), spirit or scopeof the present invention. All such modifications are intended to bewithin the scope of the claims made herein.

FIG. 1 illustrates an electrosurgical system 100 in accordance with atleast some embodiments. In particular, the electrosurgical systemcomprises an electrosurgical wand 102 (hereinafter “wand”) coupled to anelectrosurgical controller 104 (hereinafter “controller”). The wand 102comprises an elongate shaft 106 that defines distal end 108 where atleast some electrodes are disposed. The elongate shaft 106 furtherdefines a handle or proximal end 110, where a physician grips the wand102 during surgical procedures. The wand 102 further comprises aflexible multi-conductor cable 112 housing a plurality of electricalleads (not specifically shown in FIG. 1), and the flexiblemulti-conductor cable 112 terminates in a wand connector 114. As shownin FIG. 1, the wand 102 couples to the controller 104, such as by acontroller connector 120 on an outer surface 122 (in the illustrativecase of FIG. 1, the front surface).

Though not visible in the view of FIG. 1, in some embodiments the wand102 has one or more internal fluid conduits coupled to externallyaccessible tubular members. As illustrated, the wand 102 has a flexibletubular member 116 and a second flexible tubular member 118. In someembodiments, the flexible tubular member 116 is used to provideelectrically conductive fluid (e.g., saline) to the distal end 108 ofthe wand. Likewise in some embodiments, flexible tubular member 118 isused to provide aspiration to the distal end 108 of the wand.

Still referring to FIG. 1, a display device or interface panel 124 isvisible through the outer surface 122 of the controller 104, and in someembodiments a user may select operational modes of the controller 104 byway of the interface device 124 and related buttons 126.

In some embodiments the electrosurgical system 100 also comprises a footpedal assembly 130. The foot pedal assembly 130 may comprise one or morepedal devices 132 and 134, a flexible multi-conductor cable 136 and apedal connector 138. While only two pedal devices 132, 134 are shown,one or more pedal devices may be implemented. The outer surface 122 ofthe controller 104 may comprise a corresponding connector 140 thatcouples to the pedal connector 138. A physician may use the foot pedalassembly 130 to control various aspects of the controller 104, such asthe operational mode. For example, a pedal device, such as pedal device132, may be used for on-off control of the application of radiofrequency (RF) energy to the wand 102, and more specifically for controlof energy in an ablation mode. A second pedal device, such as pedaldevice 134, may be used to control and/or set the operational mode ofthe electrosurgical system. For example, actuation of pedal device 134may switch between energy levels of an ablation mode.

The electrosurgical system 100 of the various embodiments may have avariety of operational modes. One such mode employs Coblation®technology. In particular, the assignee of the present disclosure is theowner of Coblation technology. Coblation technology involves theapplication of a radio frequency (RF) signal between one or more activeelectrodes and one or more return electrodes of the wand 102 to develophigh electric field intensities in the vicinity of the target tissue.The electric field intensities may be sufficient to vaporize anelectrically conductive fluid over at least a portion of the one or moreactive electrodes in the region between the one or more activeelectrodes and the target tissue. The electrically conductive fluid maybe inherently present in the body, such as blood, or in some casesextracelluar or intracellular fluid. In other embodiments, theelectrically conductive fluid may be a liquid or gas, such as isotonicsaline. In some embodiments, such as surgical procedures on a discbetween vertebrae, the electrically conductive fluid is delivered in thevicinity of the active electrode and/or to the target site by the wand102, such as by way of the internal passage and flexible tubular member116.

When the electrically conductive fluid is heated to the point that theatoms of the fluid vaporize faster than the atoms recondense, a gas isformed. When sufficient energy is applied to the gas, the atoms collidewith each other causing a release of electrons in the process, and anionized gas or plasma is formed (the so-called “fourth state ofmatter”). Stated otherwise, plasmas may be formed by heating a gas andionizing the gas by driving an electric current through the gas, or bydirecting electromagnetic waves into the gas. The methods of plasmaformation give energy to free electrons in the plasma directly,electron-atom collisions liberate more electrons, and the processcascades until the desired degree of ionization is achieved. A morecomplete description of plasma can be found in Plasma Physics, by R. J.Goldston and P. H. Rutherford of the Plasma Physics Laboratory ofPrinceton University (1995), the complete disclosure of which isincorporated herein by reference.

As the density of the plasma becomes sufficiently low (i.e., less thanapproximately 1020 atoms/cm³ for aqueous solutions), the electron meanfree path increases such that subsequently injected electrons causeimpact ionization within the plasma. When the ionic particles in theplasma layer have sufficient energy (e.g., 3.5 electron-Volt (eV) to 5eV), collisions of the ionic particles with molecules that make up thetarget tissue break molecular bonds of the target tissue, dissociatingmolecules into free radicals which then combine into gaseous or liquidspecies. Often, the electrons in the plasma carry the electrical currentor absorb the electromagnetic waves and, therefore, are hotter than theionic particles. Thus, the electrons, which are carried away from thetarget tissue toward the active or return electrodes, carry most of theplasma's heat, enabling the ionic particles to break apart the targettissue molecules in a substantially non-thermal manner.

By means of the molecular dissociation (as opposed to thermalevaporation or carbonization), the target tissue is volumetricallyremoved through molecular dissociation of larger organic molecules intosmaller molecules and/or atoms, such as hydrogen, oxygen, oxides ofcarbon, hydrocarbons and nitrogen compounds. The molecular dissociationcompletely removes the tissue structure, as opposed to dehydrating thetissue material by the removal of liquid within the cells of the tissueand extracellular fluids, as occurs in related art electrosurgicaldesiccation and vaporization. A more detailed description of themolecular dissociation can be found in commonly assigned U.S. Pat. No.5,697,882, the complete disclosure of which is incorporated herein byreference.

In addition to the Coblation mode, the electrosurgical system 100 ofFIG. 1 may also in particular situations be useful for sealing largerarterial vessels (e.g., on the order of about 1 mm in diameter), whenused in what is known as a coagulation mode. Thus, the system of FIG. 1may have an ablation mode where RF energy at a first voltage is appliedto one or more active electrodes sufficient to effect moleculardissociation or disintegration of the tissue, and the system of FIG. 1may have a coagulation mode where RF energy at a second, lower voltageis applied to one or more active electrodes (either the same ordifferent electrode(s) as the ablation mode) sufficient to heat, shrink,seal, fuse, and/or achieve homeostasis of severed vessels within thetissue.

The energy density produced by electrosurgical system 100 at the distalend 108 of the wand 102 may be varied by adjusting a variety of factors,such as: the number of active electrodes; electrode size and spacing;electrode surface area; asperities and/or sharp edges on the electrodesurfaces; electrode materials; applied voltage; current limiting of oneor more electrodes (e.g., by placing an inductor in series with anelectrode); electrical conductivity of the fluid in contact with theelectrodes; density of the conductive fluid; and other factors.Accordingly, these factors can be manipulated to control the energylevel of the excited electrons. Because different tissue structures havedifferent molecular bonds, the electrosurgical system 100 may beconfigured to produce energy sufficient to break the molecular bonds ofcertain tissue but insufficient to break the molecular bonds of othertissue. For example, fatty tissue (e.g., adipose) has double bonds thatrequire an energy level higher than 4 eV to 5 eV (i.e., on the order ofabout 8 eV) to break. Accordingly, the Coblation® technology in someoperational modes does not ablate such fatty tissue; however, theCoblation® technology at the lower energy levels may be used toeffectively ablate cells to release the inner fat content in a liquidform. Other modes may have increased energy such that the double bondscan also be broken in a similar fashion as the single bonds (e.g.,increasing voltage or changing the electrode configuration to increasethe current density at the electrodes).

A more complete description of the various phenomena can be found incommonly assigned U.S. Pat. Nos. 6,355,032; 6,149,120 and 6,296,136, thecomplete disclosures of which are incorporated herein by reference.

FIG. 2A illustrates a perspective view of the distal end 108 of wand 102in accordance with at least some embodiments. In some embodiments, aportion of the elongate shaft 106 may be made of a metallic material(e.g., Grade TP304 stainless steel hypodermic tubing). In otherembodiments, portions of the elongate shaft may be constructed of othersuitable materials, such as inorganic insulating materials. The elongateshaft 106 may define a circular cross-section at the handle or proximalend 110 (not shown in FIG. 2), and at least a portion of the distal end108 may be flattened to define an elliptical or semi-circularcross-section.

In embodiments where the elongate shaft is metallic, the distal end 108may further comprise a non-conductive spacer 200 coupled to the elongateshaft 106. In some cases the spacer 200 is ceramic, but othernon-conductive materials resistant to degradation when exposed to plasmamay be equivalently used (e.g., glass). The spacer 200 supportselectrodes of conductive material, with illustrative active electrodelabeled 202 in FIG. 2A. Active electrode 202 defines an exposed surfacearea of conductive material, where active electrode 202 is a loop ofwire of particular diameter. For embodiments using a loop of wire, theloop of wire may be molybdenum or tungsten having a diameter between andincluding 0.025 and 0.035 inches, and more preferably of 0.030 inches,and having an exposed standoff distance away from the spacer 200 ofapproximately 0.080 inches. Spacer 200 may have a step feature 201 thatserves to limit the depth of penetration of active electrode 202 byproviding a non-conductive surface to rest on adjacent tissue, therebyallowing for a more controlled and precise cut as well as providing fora more uniform depth of thermal effect in tissue. Further, spacer 200may define an elliptical or semi-circular cross-section to provide aflattened support profile for active electrode 202.

In certain embodiments, the active electrode has an edge feature 203 ata specific, distinct location advantageous for enhanced plasmaformation. In particular, active electrode 202 may be defined by an edgefeature 203 (e.g., a scalloped portion, a cut, divot, or asperity)having a cut diameter and depth between and including 0.008 and 0.0012inches, and more preferably of approximately 0.010 inches on each side,leaving a thin segment of approximately 0.010 inches thickness in thecentral portion of active electrode 202. Referring to FIG. 2B, edgefeature 203 is preferably located in at least two positions on opposedsides of a plane P₁ bisecting the wire diameter of active electrode 202,and centered about a second plane P₂ bisecting the width of activeelectrode 202. FIG. 2C shows a cross-sectional view of active electrode202 and spacer 200 taken substantially along plane P₂ of FIG. 2B. Inparticular, FIG. 2C shows the orientation of edge feature 203 in anembodiment where the feature is a pair of symmetric cuts in activeelectrode 202. In certain other embodiments contemplated but not shown,edge feature 203 can also be a protruding section along active electrode202 formed through a coining, welding, or other forming operation toprovide exterior edges for improved localized plasma formation in theseareas. Edge feature 203 at the distal tip of active electrode 202 helpsinitiate localized plasma formation in the relative center of activeelectrode 202 for smooth cutting. Referring briefly to FIGS. 3A and 3B,active electrode 202 further has rounded edges or a smooth feature 203 bat a second, distinct location away from edge feature 203 forconductive/resistive heating of tissue at locations spaced away fromedge feature 203. In particular, active electrode 202 may be loop ofwire characterized by edge feature 203 at the apex of the loop andsmooth feature 203 b adjacent to edge feature 203 and disposed on eitherside of the loop forming active electrode 202. This conductive heatingof surrounding tissue helps provide concomitant hemostasis of smallblood vessels while plasma is initiated for cutting.

Referring again to FIG. 2A, wand 102 includes a return electrode 204 forcompleting the current path between active electrode 202 and controller104. Return electrode 204 is preferably a semi-annular member definingthe exterior of shaft 106, and a distal portion of return electrode 204is preferably exposed. Return electrode 204 is suitably connected tocontroller 104. At least a proximal portion of return electrode 204 isdisposed within an electrically insulative sheath 206, which istypically formed as one or more electrically insulative sheaths orcoatings, such as polytetrafluoroethylene, polyimide, and the like. Theprovision of the electrically insulative sheath 206 encircling over aportion of return electrode 204 prevents direct electrical contactbetween return electrode 204 and any adjacent body structure or thesurgeon. Such direct electrical contact between a body structure (e.g.,tendon) and an exposed common electrode member 204 could result inunwanted heating and necrosis of the structure at the point of contactcausing necrosis.

Return electrode 204 is preferably formed from an electricallyconductive material, usually metal, which is selected from the groupconsisting of stainless steel alloys, platinum or its alloys, titaniumor its alloys, molybdenum or its alloys, and nickel or its alloys.Referring now to FIG. 3A, the distance D between active electrode 202and return electrode 204 is preferably kept substantially constant. Assuch, it is preferred that the distal projection of return electrode 204have a non-uniform shape to approximate the geometry of active electrode202. In a preferred embodiment, return electrode 204 has an extendedfeature in the form of tab 205 extending distally. This extension tab205 maintains a near-uniform distance between the active loop electrode202 and return electrode 204. Preferably, the extended tab 205 closesthe distance between the return electrode 204 and the active electrode202 as measured at the apex of the active loop electrode 202, therebykeeping the distance D between all portions of the active and returnelectrodes substantially constant. It also brings the distal end of thereturn electrode 204 closer to the targeted tissue to improve theconduction of current through tissue and saline between the active andreturn electrodes. This enables a more uniform and continuous deliveryof electrical current through the targeted tissue during coagulationmode, providing greater depth of thermal penetration for improvedcoagulation of blood vessels.

In some embodiments saline is delivered to the distal end 108 of wand,possibly to aid in plasma creation. Referring again to FIGS. 2A and 2B,discharge apertures 208 are illustrated on the distal end 108 spacedproximally from return electrode 204. Discharge apertures 208 are formedat the distal most point of the insulative sheath 206 encircling aportion of return electrode 204. Insulative sheath 206 further createsan annular gap between the insulative sheath and return electrode 204,in which multiple axially disposed ribs are spaced equally throughout toform a plurality of fluid flow channels 209 that direct dischargedconductive fluid toward the return electrode 204 and active electrode202. Discharge apertures 208 characterize the distal most opening of theassociated plurality of flow channels 209. In the particular embodimentillustrated, eight discharge apertures are shown, but fewer or greaternumbers of discharge apertures are contemplated. The discharge apertures208 are fluidly coupled to the flexible tubular member 116 (FIG. 1) byway of a fluid conduit within the wand 102. Thus, saline or other fluidmay be pumped into the flexible tubular member 116 (FIG. 1) anddischarged through the plurality of fluid flow channels 209 anddischarge apertures 208 to further aid in developing consistent wettingaround the circumference of return electrode 204.

In yet still further embodiments, aspiration is provided at the distalend 108 of the wand 102. FIG. 3B illustrates aspiration aperture 207(i.e., suction port 207) at the distal end 108 of the device anddisposed through the non-conductive spacer 200 and defining in part anopening in return electrode 204. Suction port 207 is disposed at distalend 108 and in certain embodiments preferably only located on one sideof spacer 200 and disposed on an inferior surface of spacer 200 (suchthat when in use the suction port 207 is preferably disposed inferiorlywith regard to the angle of approach to the target tissue), andaccordingly may be disposed on the opposite side of spacer 200 from tab205. Suction port 207 aspirates the area near the distal end 108, suchas to remove excess fluids and remnants of ablation. The location ofsuction port 207 further provides for ample wetting of the active andreturn electrodes on the opposing side of the tip, with the salineflowing down from discharge apertures 208 on the non-suction side of theshaft, around the active electrode tip, then pulled back up on theinferior side of the wand with suction port 207. Applicants have foundit is particularly beneficial to direct conductive fluid flow todiscrete areas away from the suction port 207 to provide broader wettingof the exposed surface of return electrode 204, enabling more uniformplasma formation.

Additionally, referring briefly to both FIGS. 2B and 3B, suction port207 may be offset inferior from plane P₁, which also bisects thethickness T of distal end 108 of elongate shaft 106. FIG. 3C shows across-section view taken substantially along plane P₁ of FIG. 2B. Inparticular, FIG. 3C shows suction port 207 as well as spacer fluidconduit 210 defined by walls 212. Fluid conduit 210 further comprises anaspiration chamber 216 having a fluid conduit opening 214. In operation,suction is provided to the flexible tubular member 118 (FIG. 1), andflexible tubular member 118 either extends into the internal volume ofthe wand 102 to become, or fluidly couples to, opening 214 of aspirationchamber 216. Thus, conductive fluid, molecularly dissociated tissue, aswell as tissue pieces are drawn through the suction port 207, into thefluid conduit 210, and eventually through aspiration chamber 216 andopening 214. Aspiration chamber 216 is spaced proximally from suctionport 207, and the inventors of the present specification have found thata particular depth of aspiration chamber 216 and width of opening 214work better than others. For example, without the increased area ofaspiration chamber 216, the fluid conduit 210 may be subject toclogging. Likewise, if the coupling point for flexible tubular member118 at opening 114 does not have an increased diameter, clogging mayoccur. In accordance with at least some embodiments, the nature of fluidconduit 210 transitions over a length L between suction port 207 andopening 214. The entrance to the fluid conduit 210 is referenced by anaspiration aperture width W_(a). In accordance with at least someembodiments the internal walls 212 that define fluid conduit 210smoothly transition to a change in width referenced by an opening widthW_(o) at opening 214 over length L wherein the width change to W_(o) atopening 214 should be at least half the full ID of the shaft.Additionally, referring again now to FIG. 2C, the depth of fluid conduit210 as it transitions to aspiration chamber 216 should smoothly vary atleast to a depth referenced by depth D_(c), wherein the apex of depthD_(c) should be at least half the thickness T (FIG. 2B) of spacer 200and then smoothly transitioning to a depth D_(o) at opening 214. Theinventors present the nature of fluid conduit 210 as described above byway of example only. Other variances and transitions in the shape,respective widths, and depths of portions of fluid conduit 210 andaspiration chamber 216 from suction port 207 to opening 214 may beequivalently used.

As shown for example in FIGS. 2A-3B, return electrode 204 is notdirectly connected to active electrode 202. To complete a current pathso that active electrode 202 is electrically connected to returnelectrode 204 in the presence of a target tissue, electricallyconducting liquid (e.g., isotonic saline) is caused to flow along liquidpaths emanating from discharge apertures 208 and contacting both returnelectrode 204 and active electrode 202. When a voltage difference isapplied between active electrode 202 and return electrode 204, highelectric field intensities will be generated at the distal tip of activeelectrode 202 with current flow from active electrode 202 to the returnelectrode 204, the high electric field intensities causing ablation oftarget tissue adjacent the distal tip of active electrode 202.

FIG. 4A shows a cross-sectional elevation view of a wand 102 inaccordance with at least some embodiments. In particular, FIG. 4 showsthe handle or proximal end 110 coupled to the elongate shaft 106. Asillustrated, the elongate shaft 106 telescopes within the handle, butother mechanisms to couple the elongate shaft to the handle may beequivalently used. The elongate shaft 106 defines internal conduit 400that serves several purposes. For example, in the embodimentsillustrated by FIG. 4 the electrical leads 402 and 404 extend throughthe internal conduit 400 to electrically couple to the active electrode202 and return electrode 204, respectively. Likewise, the flexibletubular member 116 extends through the internal conduit 400 to fluidlycouple to the plurality of flow channels 209 and discharge apertures 208via insulative sheath 206.

The internal conduit 400 also serves as the aspiration route. Inparticular, FIG. 4B illustrates suction port 207. In the embodimentsillustrated the flexible tubular member 118, through which aspiration isperformed, couples through the handle and then fluidly couples to theinternal conduit 400. Thus, the suction provided through flexibletubular member 118 provides aspiration at the suction port 207. Thefluids that are drawn into the internal fluid conduit 400 may abut theportion of the flexible tubular member 116 that resides within theinternal conduit as the fluids are drawn along the conduit; however, theflexible tubular member 116 is sealed, and thus the aspirated fluids donot mix with the fluid (e.g., saline) being pumped through the flexibletubular member 116. Likewise, the fluids that are drawn into theinternal fluid conduit 400 may abut portions of the electrical leads 402and 404 within the internal fluid conduit 400 as the fluids are drawnalong the conduit. However, the electrical leads are insulated with aninsulating material that electrically and fluidly isolates the leadsfrom any substance within the internal fluid conduit 400. Thus, theinternal fluid conduit serves, in the embodiments shown, twopurposes—one to be the pathway through which the flexible tubular member116 and electrical leads traverse to reach the distal end 108, and alsoas the conduit through which aspiration takes place. In otherembodiments, the flexible tubular member 118 may extend partially orfully through the elongate shaft 106, and thus more directly couple tothe aspiration apertures.

FIGS. 4A and 4B also illustrate that, in accordance with at least someembodiments, a portion of the elongate shaft 106 is circular (e.g.,portion 410) and another portion of the elongate shaft 106 is flattened(e.g., portion 412) to define an elliptical or semi-circularcross-section. In some embodiments, the distal 3 centimeters or less isflattened, and in some cases the last 2 centimeters. In otherembodiments, the entire elongate shaft may define the elliptical orsemi-circular cross-section. Additionally, in the particular embodimentsillustrated the angle between the axis of portion 410 and the axis ofportion 412 is non-zero, and in some embodiments the acute angle betweenthe axis of portion 410 and the axis of portion 412 is 20 degrees, butgreater or lesser angles may be equivalently used.

As illustrated in FIG. 1, flexible multi-conductor cable 112 (and moreparticularly its constituent electrical leads 402, 404 and possiblyothers) couple to the wand connector 114. Wand connector 114 couples thecontroller 104, and more particularly the controller connector 120. FIG.5 shows both a cross-sectional view (right) and an end elevation view(left) of wand connector 114 in accordance with at least someembodiments. In particular, wand connector 114 comprises a tab 500. Tab500 works in conjunction with a slot on controller connector 120 (shownin FIG. 6) to ensure that the wand connector 114 and controllerconnector 120 only couple in one relative orientation. The illustrativewand connector 114 further comprises a plurality of electrical pins 502protruding from wand connector 114. In many cases, the electrical pins502 are coupled one each to an electrical lead of electrical leads 504(two of which may be leads 402 and 404 of FIG. 4). Stated otherwise, inparticular embodiments each electrical pin 502 couples to a singleelectrical lead, and thus each illustrative electrical pin 502 couplesto a single electrode of the wand 102. In other cases, a singleelectrical pin 502 couples to multiple electrodes on the electrosurgicalwand 102. While FIG. 5 shows four illustrative electrical pins, in someembodiments as few as two electrical pins, and as many as 26 electricalpins, may be present in the wand connector 114.

FIG. 6 shows both a cross-sectional view (right) and an end elevationview (left) of controller connector 120 in accordance with at least someembodiments. In particular, controller connector 120 comprises a slot600. Slot 600 works in conjunction with a tab 500 on wand connector 114(shown in FIG. 5) to ensure that the wand connector 114 and controllerconnector 120 only couple in one orientation. The illustrativecontroller connector 120 further comprises a plurality of electricalpins 602 residing within respective holes of controller connector 120.The electrical pins 602 are coupled to terminals of a voltage generatorwithin the controller 104 (discussed more thoroughly below). When wandconnector 114 and controller connector 120 are coupled, each electricalpin 602 couples to a single electrical pin 502. While FIG. 6 shows onlyfour illustrative electrical pins, in some embodiments as few as twoelectrical pins, and as many as 26 electrical pins may be present in thewand connector 120.

While illustrative wand connector 114 is shown to have the tab 500 andmale electrical pins 502, and controller connector 120 is shown to havethe slot 600 and female electrical pins 602, in alternative embodimentsthe wand connector has the female electrical pins and slot, and thecontroller connector 120 has the tab and male electrical pins, or othercombination. In other embodiments, the arrangement of the pins withinthe connectors may enable only a single orientation for connection ofthe connectors, and thus the tab and slot arrangement may be omitted. Inyet still other embodiments, other mechanical arrangements to ensure thewand connector and controller connector couple in only one orientationmay be equivalently used. In the case of a wand with only twoelectrodes, and which electrodes may be either active or returnelectrodes as the physical situation dictates, there may be no need toensure the connectors couple in a particular orientation.

FIG. 7 illustrates a controller 104 in accordance with at least someembodiments. In particular, the controller 104 comprises a processor700. The processor 700 may be a microcontroller, and therefore themicrocontroller may be integral with random access memory (RAM) 702,read-only memory (RAM) 704, digital-to-analog converter (D/A) 706,digital outputs (D/O) 708 and digital inputs (D/I) 710. The processor700 may further provide one or more externally available peripheralbusses, such as a serial bus (e.g., I²C), parallel bus, or other bus andcorresponding communication mode. The processor 700 may further beintegral with a communication logic 712 to enable the processor 700 tocommunicate with external devices, as well as internal devices, such asdisplay device 124. Although in some embodiments the controller 104 mayimplement a microcontroller, in yet other embodiments the processor 700may be implemented as a standalone central processing unit incombination with individual RAM, ROM, communication, D/A, D/O and D/Idevices, as well as communication port hardware for communication toperipheral components.

ROM 704 stores instructions executable by the processor 700. Inparticular, the ROM 704 may comprise a software program that implementsthe various embodiments of periodically reducing voltage generatoroutput to change position of the plasma relative to the electrodes ofthe wand (discussed more below), as well as interfacing with the user byway of the display device 124 and/or the foot pedal assembly 130 (FIG.1). The RAM 702 may be the working memory for the processor 700, wheredata may be temporarily stored and from which instructions may beexecuted. Processor 700 couples to other devices within the controller104 by way of the D/A converter 706 (e.g., the voltage generator 716),digital outputs 708 (e.g., the voltage generator 716), digital inputs710 (i.e., push button switches 126, and the foot pedal assembly 130(FIG. 1)), and other peripheral devices.

Voltage generator 716 generates selectable alternating current (AC)voltages that are applied to the electrodes of the wand 102. In thevarious embodiments, the voltage generator defines two terminals 724 and726. In accordance with the various embodiments, the voltage generatorgenerates an alternating current (AC) voltage across the terminals 724and 726. In at least some embodiments the voltage generator 716 iselectrically “floated” from the balance of the supply power in thecontroller 104, and thus the voltage on terminals 724, 726, whenmeasured with respect to the earth ground or common (e.g., common 728)within the controller 104, may or may not show a voltage difference evenwhen the voltage generator 716 is active.

The voltage generated and applied between the active terminal 724 andreturn terminal 726 by the voltage generator 716 is a RF signal that, insome embodiments, has a frequency of between about 5 kilo-Hertz (kHz)and 20 Mega-Hertz (MHz), in some cases being between about 30 kHz and2.5 MHz, often between about 100 kHz and 200 kHz. In applicationsassociated with otolaryngology-head and neck procedures, a frequency ofabout 100 kHz appears most effective. The RMS (root mean square) voltagegenerated by the voltage generator 716 may be in the range from about 5Volts (V) to 1000 V, preferably being in the range from about 10 V to500 V, often between about 100 V to 350 V depending on the activeelectrode size and the operating frequency. The peak-to-peak voltagegenerated by the voltage generator 716 for ablation or cutting in someembodiments is a square wave form in the range of 10 V to 2000 V and insome cases in the range of 100 V to 1800 V and in other cases in therange of about 28 V to 1200 V, often in the range of about 100 V to 320V peak-to-peak (again, depending on the electrode size and the operatingfrequency).

Still referring to the voltage generator 716, the voltage generator 716delivers average power levels ranging from several milliwatts tohundreds of watts per electrode, depending on the voltage applied forthe target tissue being treated, and/or the maximum allowed temperatureselected for the wand 102. The voltage generator 716 is configured toenable a user to select the voltage level according to the specificrequirements of a particular procedure. A description of one suitablevoltage generator 716 can be found in commonly assigned U.S. Pat. Nos.6,142,992 and 6,235,020, the complete disclosure of both patents areincorporated herein by reference for all purposes.

In some embodiments, the various operational modes of the voltagegenerator 716 may be controlled by way of digital-to-analog converter706. That is, for example, the processor 700 may control the outputvoltage by providing a variable voltage to the voltage generator 716,where the voltage provided is proportional to the voltage generated bythe voltage generator 716. In other embodiments, the processor 700 maycommunicate with the voltage generator by way of one or more digitaloutput signals from the digital output 708 device, or by way of packetbased communications using the communication device 712 (connection notspecifically shown so as not to unduly complicate FIG. 8).

FIG. 7 also shows a simplified side view of the distal end 108 of thewand 102. As shown, illustrative active electrode 202 of the wand 102electrically couples to terminal 724 of the voltage generator 716 by wayof the connector 120, and return electrode 204 electrically couples toterminal 726 of the voltage generator 716.

FIG. 8 shows a method in accordance with at least some embodiments. Inparticular, the method starts (block 800) and proceed to: flowing aconductive fluid within a fluid conduit disposed within aelectrosurgical wand, the conductive fluid discharges through aplurality of discharge apertures and flows past a return electrodedisposed distally from the fluid conduit, and is then discharged over anactive electrode (block 802); applying electrical energy between theactive electrode and the return electrode (block 804); forming,responsive to the energy, a localized plasma proximate to an edgefeature disposed on the active electrode (block 806); ablating, by thelocalized plasma, a portion of a target tissue proximate to the edgefeature (block 808); and heating, responsive to the energy, the targettissue at locations spaced away from the edge feature to thereby provideconcomitant hemostasis (block 810). And thereafter the method ends(block 812).

The above discussion is meant to be illustrative of the principles andvarious embodiments of the present invention. Numerous variations andmodifications possible. For example, while in some cases electrodes weredesignated as upper electrodes and lower electrodes, such a designationwas for purposes of discussion, and shall not be read to require anyrelationship to gravity during surgical procedures. It is intended thatthe following claims be interpreted to embrace all such variations andmodifications.

While preferred embodiments of this disclosure have been shown anddescribed, modifications thereof can be made by one skilled in the artwithout departing from the scope or teaching herein. The embodimentsdescribed herein are exemplary only and are not limiting. Because manyvarying and different embodiments may be made within the scope of thepresent inventive concept, including equivalent structures, materials,or methods hereafter though of, and because many modifications may bemade in the embodiments herein detailed in accordance with thedescriptive requirements of the law, it is to be understood that thedetails herein are to be interpreted as illustrative and not in alimiting sense.

What is claimed is:
 1. An electrosurgical wand comprising: an elongateshaft that defines a handle end and a distal end, the distal enddefining a thickness; a connector comprising a first and secondelectrical pins; an insulative sheath characterized by a plurality ofdischarge apertures on the distal end of the elongate shaft, theplurality of discharge apertures fluidly coupled to a first fluidconduit, and the first fluid conduit within the elongate shaft; a firstactive electrode of conductive material disposed on the distal end ofthe elongate shaft the first active electrode having an edge feature,and the first active electrode electrically coupled to the firstelectrical pin; a first return electrode of conductive material, thefirst return electrode comprising an extended feature disposed asubstantially constant distance from a distal apex of the first activeelectrode, and the first return electrode electrically coupled to thesecond electrical pin; and an aspiration aperture on the distal end ofthe elongate shaft fluidly coupled to a second fluid conduit, the secondfluid conduit within the elongate shaft and wherein the aspirationaperture is offset from a plane that bisects the distal end thickness ofthe elongate shaft.
 2. The electrosurgical wand of claim 1 wherein theedge feature is at least one selected from the group consisting of: ascalloped portion, a cut, a divot, and an asperity.
 3. Theelectrosurgical wand of claim 1 wherein the edge feature comprises acut, the cut has a diameter and a depth on each side between andincluding 0.008 and 0.012 inches.
 4. The electrosurgical wand of claim 1wherein the edge feature comprises a cut, the cut has a diameter and adepth on each side of 0.010 inches.
 5. The electrosurgical wand of claim1 wherein the edge feature comprises a first and second cut disposed onopposed sides of the first active electrode.
 6. The electrosurgical wandof claim 1 wherein first active electrode further comprises a loop ofwire.
 7. The electrosurgical wand of claim 6 wherein the loop of wirehas a diameter between and including 0.025 and 0.035 inches.
 8. Theelectrosurgical wand of claim 6 wherein the loop of wire has a diameterof 0.030 inches.
 9. The electrosurgical wand of claim 1 wherein thenon-conductive spacer comprises a step feature operable to limit atissue penetration depth of the first active electrode.
 10. Theelectrosurgical wand of claim 1 wherein the extended feature comprises atab.
 11. The electrosurgical wand of claim 1 wherein the plurality ofdischarge apertures are fluidly coupled to a plurality of fluid flowchannels disposed in an annular gap between the insulative sheath andthe elongate shaft.
 12. The electrosurgical wand of claim 1 wherein theplurality of discharge apertures encircle the elongate shaft.
 13. Theelectrosurgical wand of claim 1 wherein the plurality of dischargeapertures are spaced proximally from a distal-most tip of the firstreturn electrode.
 14. The electrosurgical wand of claim 1 wherein theaspiration aperture defines an aperture width, and wherein a spacerfluid conduit transitions in width from the aperture width to a fluidconduit opening width not less than half an internal diameter of theshaft.
 15. The electrosurgical wand of claim 14 wherein the spacer fluidconduit further transitions in depth from an aspiration chamber depthnot less than half a thickness of a non-conductive spacer to a fluidconduit opening depth.
 16. A system comprising: an electrosurgicalcontroller, the electrosurgical controller configured to produce radiofrequency (RF) energy at an active terminal with respect to a returnterminal; an electrosurgical wand coupled to the electrosurgicalcontroller, the electrosurgical wand comprising: an elongate shaft thatdefines a handle end and a distal end; an insulative sheathcharacterized by a plurality of discharge apertures on the distal end ofthe elongate shaft, the plurality of discharge apertures fluidly coupledto a first fluid conduit, and the first fluid conduit within theelongate shaft; a first active electrode of conductive material disposedon the distal end of the elongate shaft; wherein the first activeelectrode has an edge feature, and the first active electrodeelectrically coupled to the first electrical pin; a first returnelectrode of conductive material, the first return electrode comprisingan extended feature disposed a substantially constant distance from adistal apex of the first active electrode, and the first returnelectrode electrically coupled to the second electrical pin; and anaspiration aperture on the distal end of the elongate shaft; theaspiration aperture having an aperture width and fluidly coupled to aspacer fluid conduit, the conduit transitioning in width from theaperture width to a fluid conduit opening width not less than half aninternal diameter of the shaft.
 17. The electrosurgical wand of claim 16wherein the edge feature is at least one selected from the groupconsisting of: a scalloped portion, a cut, a divot, and an asperity. 18.The electrosurgical wand of claim 16 wherein the edge feature comprisesa cut, the cut has a diameter and a depth on each side between andincluding 0.008 and 0.012 inches.
 19. The electrosurgical wand of claim16 wherein the edge feature comprises a cut, the cut has a diameter anda depth on each side of 0.010 inches.
 20. The electrosurgical wand ofclaim 16 wherein first active electrode further comprises a loop ofwire.
 21. The electrosurgical wand of claim 20 wherein the loop of wirehas a diameter between and including 0.025 and 0.035 inches.
 22. Theelectrosurgical wand of claim 20 wherein the loop of wire has a diameterof 0.030 inches.
 23. The electrosurgical wand of claim 16 wherein theextended feature comprises a tab.
 24. The electrosurgical wand of claim16 wherein the plurality of discharge apertures are fluidly coupled to aplurality of fluid flow channels disposed in an annular gap between theinsulative sheath and the elongate shaft.
 25. The electrosurgical wandof claim 16 wherein the plurality of discharge apertures encircle theelongate shaft.
 26. The electrosurgical wand of claim 16 wherein theplurality of discharge apertures are spaced proximally from adistal-most tip of the first return electrode.
 27. A method comprising:flowing a conductive fluid within a fluid conduit disposed within aelectrosurgical wand, wherein the conductive fluid discharges through aplurality of discharge apertures flows past a return electrode disposeddistally from the fluid conduit over an active electrode, and is thenaspirated though an aspiration aperture that is offset from a plane thatbisects the thickness of the active electrode; applying electricalenergy between the active electrode and the return electrode; forming,responsive to the energy, a localized plasma proximate to an edgefeature disposed on the active electrode; ablating, by the localizedplasma, a portion of a target tissue proximate to the edge feature; andheating, responsive to the energy, the target tissue proximate to asmooth feature disposed on the active electrode at locations spaced awayfrom the edge feature to thereby provide concomitant hemostasis.
 28. Themethod of claim 27 wherein flowing further comprises flowing theconductive fluid such that the conductive fluid is discharged at leastpartially toward the active electrode in the form of loop of wire. 29.The method of claim 27 wherein the aspiration aperture is fluidlyconnected with a fluid conduit in the electrosurgical wand, theaspiration aperture distal to the plurality of discharge apertures. 30.The method of claim 27 wherein the return electrode comprises anextended feature disposed a substantially constant distance from adistal apex of the active electrode.
 31. An electrosurgical wandcomprising: an elongate shaft that defines a handle end and a distalend; a connector comprising first and second electrical pins; a firstactive electrode of conductive material disposed on the distal end ofthe elongate shaft, the first active electrode is electrically coupledto the first electrical pin; wherein the first active electrode has anedge feature at a first discrete location, and a smooth feature at asecond discrete location; and a first return electrode of conductivematerial, the first return electrode electrically coupled to the secondelectrical pin; and an aspiration aperture on the distal end of theelongate shaft, defining an aspiration aperture width and wherein theaspiration aperture is fluidly connected with a spacer fluid conduit,the conduit transitioning in width from the aperture width to a fluidconduit opening width that is not less than half an internal diameter ofthe shaft.
 32. The electrosurgical wand of claim 31, wherein the edgefeature is operable to ablate tissue, and wherein the smooth feature isoperable to heat tissue for concomitant hemostasis.
 33. Theelectrosurgical wand of claim 31, wherein the aspiration aperture islocated on only one side of the elongate shaft and is disposed on aninferior surface of a non-conductive spacer supporting the first activeelectrode.
 34. An electrosurgical wand comprising: an elongate shaftthat defines a handle end and a distal end; a connector comprising firstand second electrical pins; an insulative sheath characterized by aplurality of discharge apertures on the distal end of the elongateshaft, the plurality of discharge apertures fluidly coupled to a firstfluid conduit, and the first fluid conduit within the elongate shaft; afirst active electrode of conductive material disposed on the distal endof the elongate shaft, the first active electrode electrically coupledto the first electrical pin, and having an edge feature; anon-conductive spacer disposed adjacent the first active electrode, thespacer comprising a step feature operable to limit the tissuepenetration depth of the first active electrode; a first returnelectrode of conductive material, the first return electrode comprisingan extended feature disposed a substantially constant distance from adistal apex of the first active electrode, and the first returnelectrode electrically coupled to the second electrical pin; and anaspiration aperture on the distal end of the elongate shaft fluidlycoupled to a second fluid conduit, the second fluid conduit within theelongate shaft.
 35. An electrosurgical wand comprising: an elongateshaft that defines a handle end and a distal end; a connector comprisinga first and second electrical pins; an insulative sheath characterizedby a plurality of discharge apertures on the distal end of the elongateshaft, the plurality of discharge apertures fluidly coupled to a firstfluid conduit, and the first fluid conduit within the elongate shaft; afirst active electrode of conductive material disposed on the distal endof the elongate shaft, the first active electrode electrically coupledto the first electrical pin and including an edge feature; a firstreturn electrode of conductive material, the first return electrodecomprising an extended feature disposed a substantially constantdistance from a distal apex of the first active electrode, and the firstreturn electrode electrically coupled to the second electrical pin; andan aspiration aperture on the distal end of the elongate shaft fluidlycoupled to a second fluid conduit, the second fluid conduit within theelongate shaft; and wherein the aspiration aperture defines an aperturewidth, and wherein a spacer fluid conduit transitions in width from theaperture width to a fluid conduit opening width not less than half aninternal diameter of the shaft.
 36. The electrosurgical wand of claim 35wherein the spacer fluid conduit further transitions in depth from anaspiration chamber depth not less than half a thickness of anon-conductive spacer to a fluid conduit opening depth.
 37. A systemcomprising: an electrosurgical controller, the electrosurgicalcontroller configured to produce radio frequency (RF) energy at anactive terminal with respect to a return terminal; an electrosurgicalwand coupled to the electrosurgical controller, the electrosurgical wandcomprising: an elongate shaft that defines a handle end and a distalend; an insulative sheath characterized by a plurality of dischargeapertures on the distal end of the elongate shaft, the plurality ofdischarge apertures fluidly coupled to a first fluid conduit, and thefirst fluid conduit within the elongate shaft; a first active electrodeof conductive material disposed on the distal end of the elongate shaft,the first active electrode electrically coupled to the first electricalpin and including an edge feature; a first return electrode ofconductive material, the first return electrode comprising an extendedfeature disposed a substantially constant distance from a distal apex ofthe first active electrode, and the first return electrode electricallycoupled to the second electrical pin; and an aspiration aperture on thedistal end of the elongate shaft fluidly coupled to a second fluidconduit, the second fluid conduit within the elongate shaft and whereinthe aspiration aperture is offset from a plane that bisects thethickness of the distal end of the elongate shaft.